Earthworm casts as an alternate carrier material for biofertilizers: Assessment of endurance and viability of Azotobacter chroococcum, Bacillus megaterium and Rhizobium leguminosarum

Vermicast was used with lignite in different combinations (0:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 and 1:0) as carrier substrate for biofertilizers (Azotobacter chroococcum, Bacillus megaterium and Rhizobium leguminosarum). The viability count of biofertilizer organisms in stored carrier material was individually carried out once in 15 days for a total period of ten months. More than 1 × 107 g−1 viable cells of A. chroococcum, B. megaterium and R. leguminosarum were observed in 4:1, 5:1, 6:1 and 1:0 combination of carrier materials (vermicast:lignite) at the end of 10th month. In case of lignite carrier material, no viable cells were observed in 107 g−1 at the end of 6th month for A. chroococcum and R. leguminosarum and 5th month for B. megaterium. The correlation of viable cells of the biofertilizers was negative with reference to incubation period. The increase of vermicast proportion in carrier materials showed increase in the survival rate. The results of the present study suggest that the vermicasts can be used as an alternate carrier material for A. chroococcum, B. megaterium and R. leguminosarum.